The present invention relates to a cardiac valve prosthesis and more particularly refers to a mechanical cardiovascular valve of the type comprising a plurality of leaflets as means for closing and opening the valve.
It is well known in the cardiovascular medical technology to provide heart valve prothesis designed to replace defective and/or diseased natural cardiac valves. A cardiac valve must allow the blood flow to freely circulate there through when in an open position and must prevent blood back flow through the valve when the same is closed. These are basically the functions of a natural cardiac valve and the same objectives must be accomplished by any prosthetic heart valve. Many shortcomings and drawbacks of the several attempts made to obtain a heart valve prosthesis have caused to fail in providing a mechanical valve capable of resembling a natural heart valve and complying with the functions thereof. This is mainly due to the fact that the fluid under processing, the blood, is not a fluid like any other one, instead, the blood is a very delicate tissue that is able to be spoiled by even minor undue treatment caused, for instance, by turbulence and high shear stresses in the flow that can either produce thrombosis or emboli at local regions of stagnation, for example.
Several prosthetic heart valve mechanisms have been developed in an attempt to comply with the above remarked requirements without the mentioned drawbacks and failures. These valves typically are comprised of a valve body that accommodate valve members such as a single occluder or a plurality of occulders consisting of articulated or pivoting leaflets, for example. In other types of valves the occluder consists of a ball located in a cage, also known as ball-in-cage valves, wherein the ball is capable of seating against a seat of the valve body to close the pass through the valve, and moving away from the seat to open the valve. In some valves, members are provided that are capable of pivoting around fixed shafts or movable shafts, and some valves have been developed to have some freedom by altering the leaflet position relative to the central axis of the valve, always to improve the desired washing effect of such areas where the blood flow is zero and the blood remains stationary, also known as xe2x80x9cdead areasxe2x80x9d.
U.S. Pat. No. 4,274,437 to Lens S. Watts discloses a heart valve prosthesis comprising leaflets that both pivot and gradually orbit about an axis of the valve thus eliminating localized wear which otherwise occur at the locations in the valve body against which the rotating pivot would bear. It is not clearly disclosed, however, how the necessary forces are generated and applied to the leaflets for producing the orbiting about the axis of the valve. Moreover, leaflets do not open fully and there is no solution provided for eliminating turbulence and drag forces when the valve is open.
U.S. Pat. No. 5,197,980 to Jury V. Gorshkov discloses a cardiac valve prosthesis having valve members that open and close freely and rotate simultaneously around the body axis. The object of this invention is to produce additional back swirling of the blood flows forcing the valve members to rotate about the body axis and to intensively flush the prosthesis components by means of forward and reverse blood flows, thereby effectively improving the resistance to a thrombus formation. Again, this valve does not open in a fully mode to provide complete pass to the blood and does not provide a solution to the prevention of turbulence and drag forces when the valve is open.
U.S. Pat. No. 5,861,029 to Sergey Evdokimov discloses a heart valve prosthesis having leaflets with an additional degree of freedom, wherein the leaflets have the possibility of rotating around a central axis of an annular body. The problem underlying the invention is to create a heart valve prosthesis comprising a hinge mechanism that holds the leaflets within the valve body. This patent attempts to prevent thrombus formation by eliminating localized stagnation zones inaccessible to blood washing, and improve the hemodynamic characteristics of the valve prosthesis and extend its lifetime. This valve does not provide a full opening thereof and does not provide a solution to the turbulence and drag forces when the valve is open.
It is well known that the key of a hemodynamic flow in a natural valve is the ability to produce non turbulent flow. Natural valves open fully to provide a complete section pass and offer little or no resistance to the flowing fluid. There are no dead areas wherein blood flow stagnates and may coagulate. Further, there are no areas of turbulent flow that can damage the red blood cells and the platelets.
Unfortunately, the prior art valves still suffer from dead areas and turbulent flow. In the fully open position leaflets form an angle with the flow to assure proper closing of the valve upon dropping of the blood pressure and reversing of the blood flow during the diastolic movement of the cardiac cycle. Alternatively, the leaflets may hang parallel to the blood flow in the open position but with their downstream edges curved slightly to favour closing during diastolic cycle.
The dilemma is that a rapid valve closure has been obtained till now at the price of more turbulence and drag forces.
It is therefore an object of the present invention to provide a mechanical valve with minimal or no turbulence and minimal or no drag forces generated in the open position of the valve during the systolic pulse of the heart cycle.
It is still another object of the present invention to provide a mechanical heart valve having at least two leaflets rotating around a central axis of an annular body of the valve when the valve is not in a closed position.
Accordingly, the present invention provides a prosthetic heart valve comprising an annular body having an inner surface and an outer surface and defining a central axis of the annular body, at least two leaflets pivotally mounted to said annular body, the leaflets including pivoting means connecting the leaflets together and to the inner surface of the annular body, the pivoting means defining a pivoting axis dividing each leaflet in two sectors, one sector larger than the other, whereby the blood flow impinging onto the larger sector of each leaflet causes the leaflet to pivot around the pivoting axis and rotate around the central axis so as to define a uniform and axial flow in the blood passing through the valve.
It has been found that leaflets rotating around the central axis of the annular body are effective to eliminate the turbulent flow and drag forces when the valve is not in the closed position.
Preferably, the pivoting axis extends normally to the central axis.
The pivoting means may also comprise a central axis shaft connected to the annular body, a rotary sleeve freely mounted around the central shaft, the sleeve having radially extending pins, and each leaflet being rotatably mounted to each pin whereby each pin defines the pivoting axis for the associated leaflet.
The above and other objects, features and advantages of the present invention will be better understood when taken in connection with the accompanying drawings and description.